[200q20v] Too many error codes-where to start?

[Rich Andrews]

Start by clearing the error codes and checking the turbo bypass valve 
vacuum hoses.  I would bet that the bypass valve vacuum hose is bad and 
that would cause it to stall. I would probably replace all of the small 
vacuum hoses at the rear of the intake manifold.  Also check all of the 
hoses for excessive softness or collapse.  I assume that it starts OK 
and it idles ok.  Try this:  Get on an open stretch of road.  In 5th 
gear at 1500 RPM apply full throttle.  What is your boost at 2000 RPM?
At 2500RPM? at 3200 RPM?  Did you ever change the intercooler to intake 
manifold hose?  That would cause all manner of problems.  You have to 
take it off to check it.

rich


Forhan, Thomas wrote:

> Ran the engine diagnostics sequence this morning, which produced the
> following codes:
> 2121 - idle switch
> 4431 - idle stabilization valve
> 2342 - O2 sensor
> 4442 - waste gate frequency valve
> 
> I also see that if you have the VAG tool you get more than just the blink
> codes, because the Bentley notes further diagnostics is available in the VAG
> display "in [addition] to the component". Of cousre, I have no access to
> that.
> 
> Here is the background:
> 
> Bought the car with 125K miles  last year from a dealer, clearly
> (whooee!)some previous owner chipped it.  The car is much, much faster than
> my old 90 200 TQ IA Stage I, and a friend with an S4 commented that it is
> much, much faster than his stock S4. But no markings on the outside of the
> ECU though bag cut and retaped nicely. Maximum boost indicated on factory
> gauge is 2.4 bar, for what it is worth. 
> 
> The problem is that the car occassionally stalls coming to a stop and always
> misses during low rpm acceleration, once rpms are up about 3000 rpm it feels
> normal.
> 
> First diagnosis run about two months ago: I got a 4431 and replaced the idle
> stabilization valve, and cleaned all relevant contacts. No change.
> 
> Just about then the turbo boost valve thread started here, and the symptoms
> discussed seemed exactly like my problem. I replaced the TBV and hose and
> the problem went away for about two weeks, and then returned. I replaced
> with another new TBV, and there was no change.
> 
> So I ran the diagnostics again, and there are so many errors I don't know
> where to start. Is there a common thread above? 
> 
> Unfortunately,  I am a parts replacer, not a mechanic. Between this and the
> no heat (which I am working on, thanks) my wife is getting very skeptical of
> this purchase for a "family car"
> 
> Thanks
> 
> Tom F.
> 1991 200Q20V Avant
> 
> 
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